Question

Which is the second heart of the human body?

Answer 1

Hint: Humans have only one heart anatomically. The calf muscles (soleus muscles) are known as the "second heart" because they are important for returning venous blood from the periphery to the heart.

Complete answer:
Your calf veins serve as a storage for blood that your body does not require in circulation at any given time. Muscle venous sinuses are the veins that serve as reservoirs. Blood is squeezed out of veins and moved along the venous system as the calf muscle contracts. Leg veins have one-way valves that keep blood flowing in the right path toward the heart. These valves also prevent blood from flowing backwards down your legs veins due to gravity.
When you walk, your foot also contributes to the pumping process. There is also a (smaller) venous reservoir in the foot. The foot venous reservoir blood is squeezed out and ‘primes' the calf reservoir during the early motion of taking a stride, as you put weight on your foot.
The calf muscle then contracts and pumps blood up the leg against gravity in the later stages of a step. The valves keep the blood flowing in the right direction and keep gravity from pulling it back down.
When you are immobile for an extended period of time, such as in an aeroplane or car seat, or sitting at a desk for hours, your calf muscle does not contract much and blood pools.
That is why walking is so beneficial to leg circulation! Walking reduces blood pooling and aids in the prevention of potentially dangerous blood clots known as deep vein thrombosis, or DVT.
In addition, due to a breakdown of the one-way valves, a disease known as venous insufficiency, sometimes known as venous reflux, blood can pool in your legs. The valves are not functioning properly in this situation, allowing blood to flow backwards down your leg.
The valves are described as "leaky". Heavy, fatigued, achy, throbbing, painful legs, ankle swelling, bulging varicose veins, cramping, itching, restless leg, skin discoloration, and even skin ulceration are all signs of venous insufficiency. Venous insufficiency is a widespread condition that affects more than 40 million people in the United States.

Note:
Leg discomfort and edoema are common symptoms of DVTs. They may or may not create any symptoms. DVTs are risky because a blood clot can break off and move through your bloodstream, eventually settling in your lungs.